[vdr] Compressing VDR recordings without losing quality.

VDR User user.vdr at gmail.com
Fri Oct 29 01:28:36 CEST 2010

> I wonder if there is an easy way to recompress
> all recordings that are not already H.264 into
> H.264 files, making them a lot smaller without
> losing any quality.

The only way to not lose quality is to keep the bitrate high,
especially for recordings with a lot of motion.  You should encode
with constant quality (CRF) set to whatever the minimum quality you
want to preserve.  You can also reduce the resolution a bit, just make
sure to maintain the aspect ratio.  Bottom line is that you will not
get smaller filesizes without making sacrifices.  Data is lost with
every encoding pass.

> Would it be easy to write a small script that
> goes through all recordings, finds out whether
> the recording is MPEG2, determines the H.264
> bitrate that produces approximately the same
> quality and calls mencoder to convert it?
> Has somebody already done that?

Like I said, you aren't going to get smaller files without making a
sacrifice.  If less filsize is most important to you then you should
focus on a target bitrate at the expensive of quality.  If quality is
most important to you then focus on a CRF value at the expensive of
more filesize.

There are way too many variables for a simple one-size-fits-all option
so you get your cake and eat it too.  Video encoding simply doesn't
work that way.  Every time data is lost, it's gone forever.  The same
is true with audio encoding as well.  Some people believe in magic,
even when there is no magic.

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